RFID systems are well known and the prior art includes different types of RFID systems, different applications for RFID systems, and different data communication protocols for RFID systems. RFID systems are commonly utilized for product tracking, product identification, and inventory control in manufacturing, warehouse, and retail environments. Briefly, an RFID system includes two primary components: a reader (also known as an interrogator); and a tag (also known as a transponder). The tag is a miniature device that is capable of responding, via an air channel, to an RF signal generated by the reader. The tag is configured to generate a reflected RF signal in response to the RF signal emitted from the reader. The reflected RF signal is modulated in a manner that conveys identification data back to the reader. The identification data can then be stored, processed, displayed, or transmitted by the reader as needed.
Due to the size and complexity of the necessary components, fixed RFID readers mounted by doorways, loading docks, and assembly lines were the first to be developed and deployed in the field. As RFID technology matures and continues to emerge as a force in the data acquisition industry, the need for mobile handheld RFID readers becomes increasingly important. Handheld RFID readers have traditionally leveraged the RF antenna designs from fixed reader equipment. In this regard, some RFID reader antennas are relatively large, heavy, and obtrusive, and other RFID antennas provide either horizontal polarization or vertical polarization. Conventional RFID tags are typically polarized in only one direction: vertical or horizontal. Therefore, a horizontally polarized RFID reader antenna is unable to accurately read a vertically polarized tag without physical manipulation or rotation of the reader and/or tag. Likewise, a vertically polarized RFID reader antenna is unable to accurately read a horizontally polarized tag without physical manipulation or rotation of the reader and/or tag.
In practice, handheld RFID-enabled products have traditionally needed to make significant design compromises, such as antenna size and performance versus product size, polarization diversity versus product size and ergonomics, and the like. There remains a need for a compact and polarization insensitive antenna design that is suitable for handheld RFID readers.